Lory: Very interesting catch there, good stroke of luck as the musical interval chimes actually belongs to
HSW Bangkok Meteo Marine Radio and is used on its transmission as an interval pause. Usually between the language change over from Thai to English or vice versa.
I have never in all my years of chasing/monitoring volmets heard
HSD Bangkok Volmet do this (10/40 past the hour) and in the Thai language, and I presume that they did not exceed their time allocation on 6.676MHz and thus lap into the next allocated stations transmission (ARA Karachi, Pakistan at 15/45 past the hour)? Pity your Kenwood TS-950SDX didn't have a GMT clock radio to show the actual recording time.
Listening to your Youtube recording is sounds very much like HSW Bangkok Meteo Marine radio giving marine weather in Thai, no mention of QNH etc.
The Asia/Pacific stations that use two 6MHz volmet channels, 6.676 and 6.679MHz USB have always transmitted their reports in English language too, including HSD Bangkok Volmet.
The above suggests to me that a station engineer made a serious transmitter error and put HSW on HSD's channel...

Maybe there was a stuff up at the transmitter site just out of Bangkok as HSW (marine section) use 6.765MHz and HSD (aviation section) 6.676MHz share the same facilities, a miss pushed button or switch thrown in the wrong position may be the net cause...

Still, a great catch!