hi,
I am 3 km away from Jomtien.
you can find very good price from 3000 baht (28sqm) to 8000 bahts(36 sqm) a month. all depends of what you want, swimming pool or not.
agencies charge too much (usually 2000 bahts more), better deal with thai people directly or go look directly at advertisement in building.Plenty of empty condo in Thailand.

I have a channel on youtube. (swissguy)

cheers