The photos, from Japan’s Himawari-8 satellite, shows Noru making landfall in Vietnam’s central coastal city of Hoi An.
GISTDA said the storm was expected to weaken into a depression before entering Thailand on Wednesday night or early Thursday.
It said Ubon Ratchathani would be the first to get pounded.
The province has already been hit by heavy rains since Tuesday night.
The National Disaster Warning Centre meanwhile announced that it had been asked by the Ubon Ratchathani disaster prevention and mitigation office to send an M11 code warning of heavy rains to all warning towers in tambons and districts.
In its 13th Noru storm warning at 11am on Wednesday, the Meteorological Department said the storm had already weakened from a typhoon into a tropical storm as it reached Salavan province in Laos at 1pm on Tuesday.
With sustained wind speeds of about 70km per hour, Noru is moving west at around 15km per hour.
The storm will weaken before passing lower Laos and Thailand’s lower Northeast in Amnat Charoen and Ubon Ratchathani on Wednesday night, then further weaken into a tropical depression and an active low pressure cell, the department added.