You can find month to month with smaller deposit . Usually they make up the difference by charging above government rate (5b ish) so anything above 5 is profit to the landlord who then pays electricity and keeps the difference. In your contract or agreement so it is legal.

Other , and most will required a 2 month deposit . So if you sign such an agreement and leave after 90 days they will keep your deposit . You must fulfill your year contract and not damage anything to receive your deposit .

I know some short term stays in Pattaya but Bangkok I can’t help. Good trip have fun ,

$2100 fixed cost in Thailand is mid-high can do much cheaper .

For a couple <$500 a room is fine

Plan your rental close to stores bars restaurants keep transportation low <$150

Phone and WiFi dtac <$30 phone with hot spot get an apartment with WiFi inc

Electric I need aircon $100

Food $300 and that’s eating well

Lots of temptation available here so can spend thousands or it’s a thousand depends on your lifestyle

A fun night out as a couple can be done for $100

Partying with ladies till the bars close can easily hit $500

There’s something for everyone and every budget in Thailand