What you can buy depends on your savings and needs. It is like buying a condo in Orchard Rd vs a condo in Woodlands. I bought in a very prime area where prices have gone up by 30% since. I like the convenience of living in such an area and the unintended prestige (the Thais will be more impressed if they know you live in a prime area, not that I care particularly).
However, if your budget is not generous, then you may look at the higher Sukhumvit area (Phra Kanong upwards) or along the existing/future BTS lines.
One thing to note, if you buy a cheap condo or apartment, your neighbours may not be so nice so you may get noise disturbance in the middle of the night etc.
So decide on the place(s) you like and have a walk around or take a motosai. If it is an existing condo, go and see the juristic office (it operates Mon to Sat half-day). It would have a list of units in that condo for sale and rent and it can put u in touch with its sales team.
Or you can search online on prakard or DDProperty.
Last, if u are putting it solely in your name, pls check with the juristic if the foreign quota is still available.