Seven crew members were reported missing and a dock worker was killed after two massive blasts tore through a small product tanker in Thailand.

The explosions hit the 6,500-dwt Smooth Sea 22 (built 2018) on Tuesday morning on the Mae Klong river, injuring four other people.

Video footage shows a first blast tearing apart the tanker and throwing a section of the vessel into the sea, before another intense blast rips through the hull, engulfing the ship in orange flames.

Plumes of black smoke are later shown billowing into the sky from the middle of the stricken tanker.

Nearby houses were damaged, with windows shattering.

The blasts were felt and heard over a radius of several kilometres.

The missing and injured are all from Myanmar and Thailand.

The Bankgkok Post cited the provincial authority as blaming welding work for the accident.

The Thai-flag tanker was undergoing maintenance at Ruammitr Dockyard.

The blaze took an hour to bring under control.

An investigation has begun.

Oil on board

The tanker had 25,000 litres of fuel oil and 20,000 litres of diesel on board, the local authority said.

The vessel is owned by Smooth Sea Co of Bangkok.

In October, a tanker owned by the same company came very close to hitting a riverside restaurant in the city.

Thai TV reported that the 7,400-dwt product tanker Smooth Sea 18 (built 2004) came within metres of crashing into a river-side establishment in the Samut Prakan area of the Thai capital.

Video footage begins with panicked shouting as diners try to warn the Thai-flag tanker as it drifts closer.