Non Imm O Visa and do 12 month extensions in Thailand.
800,000 Baht in a Thai bank or proof of 65,000 Baht monthly income for the extensions.
No need for expensive agent.
Easy to do yourself.
You do not qualify for Visa on Arival.
You do qualify for a Visa Exempt Entry giving you a stay of 30 days.
This can be extended by a further 30 days at Immigration for a fee of 1,900 Baht.
If you intend staying any longer you should apply for a Tourist Visa before you leave.
A Multi Entry Non O Visa is valid for 12 months from date of issue and gives multiple stays of up to 90 days each entry.
A maximum of 15 months stay can be obtained if used correctly.
This Visa can be obtained for a multitude of reasons including Marriage to a Thai National or Retirement if over 50.
Not possible.
All he can do is get a 30 day extension.
Or a Non Imm O Visa followed by a 12 month extension for retirement if he has 800,000 in a Thai bank.
When I did my first marriage extension 20 years ago at Samui they also required Affirmation to Marry from the Embassy.
Plus a witness who was quite happy to go with the promise of a bottle of whisky.