What should I do about my tourist visa in Thailand before starting my new job?

Question about visas: I entered Thailand on a non-b visa but things didnt work out with my first employer. I left the country and went to Laos for a border run and re-entered on a tourist visa so my second employer could convert it to a non-b. once again, things did not work out. now i have a new job that starts in mid-october but my tourist visa currently ends on september 27th. should i go to immigration and get a 30 day renewal or should i leave and re-enter again? how long should i leave for? should ask my new job for a letter to help me at the border? im afraid of being denied at the border but i would do it by air this time to another country instead of by bus like the last time.