Does the UK embassy accept an onward travel ticket by coach or mini bus for the METV application in Thailand?

no problem at all showing proof of onward travel by land. however for the METV you usually have to show your leaving Thailand after 60 days and then coming back so I don't know how you're going to show them that you need an METV AI is the worst source for accurate info about entry/visa/extension to thailand, there's so much bad info out there that if you don't ask the exact right question with the right wording you'll get outdated, wrong info that has been parroted so often the AI data mines it as real info

This is a recent post describing the METV multiple entry tourist visa... The METV multiple entry Tourist Visa is valid for use for 6 MONTHS from the date it's issued. Therefore, don't apply for it too soon. Upon your arrival into Thailand... You are stamped in for 60 days... That can be extended for 30 ADDED days at your local Thai Immigration office for 1900 Thai baht... OR... do a border bounce by land, sea or by Air.. getting a New 60-day stamp on arrival. That can be done on the same day return...with planning. As not all Land border crossings allow for same day return. One or two nights stay in the visiting country may be required. Repeat the process...get a NEW 60-day STAMP with one 30-day extension of stay. 2+1+2+1+2+1 = 9 months maximum. Be sure to leave Thailand a day or 6 prior to your stamped ending date each time. If you are going to use a BORDER BOUNCE, use an experienced border run service company to take you with a same day return. They arrange for your exit and re-entry same day. There are several fine companies who offer the same day BORDER BOUNCE services. At this time, All Cambodia land border crossings are CLOSED. AND All Myanmar land border crossings are CLOSED. There's a BORDER BOUNCE service company in Ranong, South Thailand which makes a same day BORDER BOUNCE to Myanmar and back. Flights are low prices to several SE Asian locations... Hanoi and Ho Chi Minh City Vietnam, Phnom Penh Cambodia, and Singapore...to name a few. Again, with flight schedules, same day return is possible. When you apply for the METV...show a trip departing Thailand within the first 60 or 90 days... which demonstrates the need for the METV multiple entry tourist visa. Just show desired flight date, destination, and airline. No actual ticket needed. Tod Daniels is the expert on the METV multiple entry tourist visa, in my opinion. He's advised MANY of its use on Thai Visa Advice forum.