If I am denied entry to Thailand at a land crossing and made to return to Laos (for example), will I receive any stamp/note on my passport that would be potentially detrimental should I attempt to come back to Thailand again (or any other country, for that matter)?
TLDR : Answer Summary
There is little concern about receiving a stamp or note in your passport if you are denied entry to Thailand at a land crossing; accounts of such occurrences are rare. Even if denied entry, immigration authorities primarily rely on digital records rather than physical stamps.