I fly in and out 4 or 5 times a year normally staying 1 to 2 months with a border jump, but same as you a one way ticket and pending on work when I return but never had an issue or pulled up or asked about accommodation,, but I do have a house and twin daughters there, a lot of FIFO workers fly in and out every month with no issues, so I think you will be ok.
I fly in 4 or 5 times every year and only have a 1 way ticket, because of work I don't know when I will be needed so 1 way ticket and stay until I am required with the odd border jump, but never been asked about a return ticket.
It's not America,,, tips are totally up to you, while it's nice to tip people and Thais do have a low income, but you will go broke tipping everyone for everything.
are you talking about the automatic 30 day visa on arrival?? Because I go 4 or 5 times a year and just get the arrival visa sometimes do a border run as well.
the original post states he's a tourist so i assumed he wouldn't be here longer than 3 months but i didnt read the rest of his post his licence has expired so he can't get an IDL anyway, but I'm here 1 month every 3 months, so I've never worried about going through the hassle of getting a thai licence, but maybe I should.