Vietnam. I was told that this set was Vietnamese and Munger/III 2000 lists a Vietnamese set with similarities. But Munger describes a more compatible set being from Taiwan, so I thought it must be Taiwan.
However, February 2023, an almost equal set, but now with original lacquerware board signed by "Thānh Lễy, Vietnam" appeared. So the set is indeed Vietnamese. I think Munger is not correct this time.