HiTroy,
dont know how old your father is, but I suppose over 55. From this age on it is possible to get a non-immigrant visa O. To receive it you just have to prove an income of 65000 Baht per month (approx. 1000 pounds) or 800000 Baht on a bank account here. The visa is issued for 1 year and after that you can get a new one. In my case I have to leave the Kingdom every 3 months to get a new stamp in the passport. That can be just crossing the border for 1 hour and come back.
Cost of living is quite low. Renting a house in Chiang Mai, Pattaya or Hua Hin will come up to 5000-15000 Baht per month. Eating, drinking etc. another 5000 to 10000, if you are not entertaining the girls too much or have one who is sucking your money. So there is still enough stuff for shopping, partying or traveling.
So let your dad come over here. Especially in Chiang Mai are plenty of English guys to be happy to see him.