I have a very comfy 1-bed condo in Bangsaray, about 40 sqM. 20-25k is a big lump out of a UK pension, but of course will be much bigger in Pattaya or Jomtien
Rent, don't buy. Much more flexible if you want to move. No problems getting your money out if you relocate again (to another country, or heaven or hell!) About 8-10k baht a month rent, £180-220
If you stay 180 days or more, you're a tax resident. Cumulative in any calendar year, so a border bounce on day 179 doesn't help you. You (should) declare all the money you import to Thailand. It is assessible for tax. You show tax certificates in that tax year from home country, which is deducted from tax due in Thailand. Maybe you will be able to demonstrate that you transferred savings rather than income, but the mechanics for doing that are not clear so far. Maybe it would be as simple as showing a statement showing the funds leaving your home savings account.
I applied a year ago, David. The Thai London embassy emailed me saying I should ignore the requirement for life insurance, as no longer needed. Too late, as I'd already bought it for £1,100!
If you are clear the landlord is responsible your last resort is to call a plumber, pay to get it fixed and deduct the cost from your rent. Landlord will likely deduct it from your deposit when you leave, but there's no guarantee you'd get that back anyway.