The Scout [aka Bit Pi-Pop Ta-Lu Lohk] (Thailand-2009; dir. Pleo Sirisuwan)
Scouts visit an ancient temple to witness a lunar eclipse. Hearing campfire stories of the legendary god who protects the temple, they decide to go on a treasure hunt. Finding themselves lost in a parallel universe, they must find the way back before the end of the eclipse traps them.
Here are another couple of posters, one in English:
Below are some pictures of the cast and crew (at a premiere event) and in character: