I'm looking for a private band rehearsal space that I can rent by the month or so, keep my equipment locked up in, and access 24/7. 

 

Something around the Sukhumvit neighborhood would be best. 

you should ask in some of the music shops around Bangkok.

I know for a FACT that the music shop in COCO-WALK (near to Ratchathewi BTS station) has a Rehearsal room within their shop.

Perhaps visit them and ask questions.  perhaps they know of a permanent location for you or a good suggestion.

 

also: 

around Pratunam...  opositte Panthip Plaza there is a PIZZA COMPANY.

there is a small soi with an open square area for parking cars to the LEFT SIDE of pizza company.

at the far back RIGHT side of this area is a 2nd hand music shop and repair shop.

the guy in there seems the type of guy that may know about this sort of thing.

 

other than that, you may try regular music shops, but staff may be limited knowledge.

 

also:

search and join a MUSIC BAND page on facebook and ask the question within the groups page.

 

Any idea how much this sort of thing costs? 

16 hours ago, 3WrhtgTih6gireLH said:

Any idea how much this sort of thing costs? 

i have no idea.

sorry.

you will need to find out by going there or searching more online.