I'm doing a 10.000 km (6.214 miles) bicycle ride across all 10 ASEAN countries within 100 days.

Multiple entries into Thailand from Cambodia, from Laos and from Myanmar.

Thailand 30-days visa stamp on arrival not a problem.

Just assuming that there shouldn't be any issue crossing the border, leaving a week later and re-entering

just 10 days after that again, traveling 12 days later out and returning again for 6 days before departing to Malaysia.

The in and outs are definitvely tourist visa related, besides the tour is widely covered by international media.

No information from Thai Embassy upon emails and phone calls received.

Might need to make a trip to the Royal Thai Embassy in person, unless getting an answer here

( for someone interested about details of the 10.000 km tour - here are details: http://theraod6.wix.com/asiantour )

Thank you in advance for any advice on multiple entry visa handling (without applying visa at embassy)

Where are you from? G7 countries get 30 days upon entry over land, most other countries 15. But with your plans that should not be an issue, and neither should the visa exempt entries.

Moved to the Thai visas forum.

Your entries and departures are within the rules for visa exempt entries.

As said you will only get 15 day entries unless from a G7 country.