A landlord in Thong Lo once told me he hadn't raised his rent in six years because he was afraid his tenant would leave. When I asked what he was charging for a two bedroom condo near BTS Thong Lo, he said 25,000 baht. Similar units in the same building were going for 38,000 to 42,000 baht. He was leaving close to 200,000 baht a year on the table. And he had no idea.

That story isn't unusual. Bangkok is full of landlords, both Thai and foreign, who lose serious money not because the market is bad but because they keep making the same avoidable mistakes. Let's talk about the ones that actually cost thousands.

Pricing Your Condo Based on Feelings Instead of Data

This is the single most expensive mistake Bangkok landlords make. You bought your condo at Ideo Mobi Sukhumvit for 5.2 million baht, so you feel like 30,000 baht a month is fair. But feelings don't set market rent. The neighborhood does. The floor plan does. The competition in your building does.

Overprice by even 3,000 to 5,000 baht per month and your unit sits empty. Two months of vacancy on a unit that should rent for 28,000 baht means you just lost 56,000 baht. That's worse than pricing correctly from day one, even if it felt like "less than you deserved."

On the flip side, underpricing is just as painful. I've seen a studio at The Line Ratchathewi listed at 14,000 baht when comparable units were pulling 18,000 to 19,000. That landlord was essentially donating 48,000 to 60,000 baht per year to a tenant who would have happily paid market rate.

Check what similar units in your building are actually renting for right now. Not what you listed it for three years ago. Not what your neighbor claims. Actual current market data.

Ignoring Small Maintenance Issues Until They Become Big Ones

A dripping faucet in a condo near BTS Ari seems like nothing. You tell your tenant you'll get to it next week. Next week turns into next month. Then the tenant sends you photos of water damage on the bathroom cabinet. Now you're looking at a 15,000 baht repair instead of the 800 baht washer replacement you could have handled immediately.

Bangkok's humidity makes everything worse, faster. Mold spreads in days. Small leaks warp laminate flooring within weeks. A minor aircon issue left unchecked leads to a compressor replacement that costs 12,000 to 18,000 baht.

The landlords who spend the least on maintenance long term are the ones who respond quickly to small problems. Get a reliable handyman. Put them on speed dial. I know landlords who have a go to aircon technician in the Soi Ari area and a plumber near On Nut who can show up same day. That kind of network saves you real money over time.

And here's the hidden cost of ignoring repairs. Your tenant leaves. Unhappy tenants don't renew. Another month of vacancy, another 25,000 to 35,000 baht gone.

Skipping Proper Tenant Screening

A landlord with a one bedroom at Life Asoke Hype once rented to the first person who showed up with cash. No passport copy, no employment verification, no questions asked. Within four months, the tenant disappeared owing two months of rent and left the unit in a condition that required nearly 40,000 baht in cleaning and repairs.

Bangkok moves fast and it's tempting to fill a vacancy the moment someone shows interest. But rushing this step is where landlords get burned the hardest. Proper screening means collecting ID, asking for proof of employment or a letter from their company, and checking references from previous landlords if possible.

For expat tenants, find out visa status and how long they plan to stay. A tenant on a tourist visa "planning to extend" is a very different risk profile than someone with a work permit at a company in Sathorn. Take the extra day to verify. That one day of caution can save you months of headaches.

Writing Weak Lease Agreements

Too many Bangkok landlords use a one page lease they found online or, worse, rely on a verbal agreement. Then when disputes happen, and they do happen, there's nothing to fall back on.

I've seen a case near MRT Phra Ram 9 where a landlord couldn't collect on damages because the lease had no clause about the security deposit conditions. The tenant argued the scuffed floors were "normal wear and tear" and the landlord had no contractual language to counter it. The deposit refund dispute cost more in time and stress than the 20,000 baht at stake.

Your lease should clearly cover deposit terms and deduction conditions, early termination penalties, maintenance responsibilities for both parties, utility payment procedures, and what happens if rent is late. Get a proper bilingual lease reviewed by someone who understands Thai tenancy norms. It costs a few thousand baht upfront and protects tens of thousands down the road.

Not Treating Your Rental Like a Business

Your condo at Lumpini Suite Phetchaburi near MRT Makkasan isn't just a property. It's an income generating asset. Yet many landlords treat it like a personal favor to the tenant rather than a business relationship.

That means they don't track expenses, don't document the unit's condition at move in and move out, don't keep receipts for repairs, and don't review their rental price annually. Over five years, this casual approach can quietly drain hundreds of thousands of baht through mispricing, preventable damage, and poor tenant retention.

Take 30 minutes each quarter to review your numbers. Are you charging market rate? Is your tenant happy enough to renew? Are there deferred maintenance items creeping up? Small check ins prevent big losses.

Owning a rental condo in Bangkok can be genuinely profitable, but only if you treat it with the same attention you'd give any other investment. The landlords who do well here aren't lucky. They're just disciplined about the basics. If you want help pricing your unit accurately, finding quality tenants, or simply understanding what your condo is worth in today's market, check out superagent.co for data driven tools built specifically for Bangkok rentals.