@Gregg ************
Yes, it's one border crossing many people overlook or don't realize is there. There are actually two checkpoints rolled into one - the first one is for local Thais and Burmese only, for the small, older casino on the opposite bank.
The big one, open to everyone is the Golden Triangle Economic Zone one, which is designed to allow gamblers across from Chiang Rai. The opening hours aren't as long as Chiang Khong, but it may be an alternative for those who don't want to go to the latter for whatever reason. Even though you have to catch a boat, it may be quicker than waiting for the bus at the Chiang Khong crossing and again on the way back.