The floodwaters have inundated many stores in Rim Moei Market. Residents were also forced to monitor the flood situation overnight.
Myanmar people on the public island under the first Thai-Myanmar Friendship Bridge were forced to evacuate to the Thailand side.
Meanwhile, Chinese casino operators on the Myanmar side also have moved their belongings to higher ground.
The Thailand Meteorological Department had earlier forecast heavy to very heavy rain in 43 provinces, mainly in the North, Northeast and Eastern regions.
This is likely to cause sudden floods and flash floods, especially in hilly and low-lying areas, the department said, adding that Bangkok would also see downpours, with 60% of the area affected.