Sadly, Thai coach's fault! He claimed a video challenge on the Japanese player who touched the Thai court with her hands while diving. He doesn't know the regulations. It is allowed to touch the opponents' court with any part of the body above the foot. Even the foot can touch the opponents' court if a part of it still stays on top of the centre line. The referee couldn't allow such a challenge. That is probably what the video challenge team said "It is not allowed". They didn't mean the Thai coach lost the right to challenge, but that particular challenge is not allowed.