It depends on the property, the location, and what you're comparing it against -- there isn't a single yes-or-no answer, and be wary of anyone who gives you one without knowing your specific situation.
On the positive side, condos are the simplest property type for foreigners to own outright, rental demand in areas like Pattaya is driven by steady tourism and a growing expat and long-stay community, and rental yields in the 5% to 8% range are commonly cited for well-located units, though actual returns vary a lot by building, unit type, and management.
On the other side, it's worth going in with realistic expectations: liquidity is generally lower than in most buyers' home property markets, meaning a resale can take longer to find a buyer than you might expect. Currency movements between your home currency and Thai baht can affect your real return if you're comparing it back to your own currency. Some areas and building types have seen oversupply, which affects both rental competition and resale pricing. And a condo's ongoing costs -- common area fees, sinking fund contributions, and maintenance -- need to be factored into any yield calculation, not just the headline rental income.
The properties that tend to perform best as investments are usually well-located, well-managed buildings with genuine rental demand, rather than the cheapest unit available. This isn't financial advice, and your own circumstances, goals, and risk tolerance matter more than any general rule of thumb -- it's worth discussing your specific plans with an independent financial adviser alongside any property research.