@Chris ********
Assuming he's UK passport holder, doesn't need a visa. Can enter visa free for 30 days. With at least 15 days still outstanding on the entry stamp he can apply for a Non-O (over 50) visa. Conditions for this vary from office to office. In Bangkok they want to see the 800,000 baht in a Thai bank account and a 12-month lease. Once he's got the 90-dayer, he can apply close to the expiry for a 12-month visa extension with similar criteria as the 90-dayer. There are no Multi-Entry visas issued in Thailand. He simply gets a Multi-Entry Re-entry Permit