Election staff rushed to protect ballots as a storm battered a voting booth during sham elections in northern Thailand.

Footage shows the officers grabbing several documents as heavy rain pummeled the poll station in Chiang Rai province just hours before voting closed on May 14.

Thananya, member of the election committee in Chiang Rai's Constituency 7, said: 'At around 3 PM, the storm struck. I took a video as evidence in case there was any mistake in the results. The officers were doing their best to protect the documents to prevent them from being damaged.'

The Thai Meteorological Department issued a weather advisory on May 14 warning that tropical cyclone Mocha was expected to bring persistent rainfall to northern Thailand, with heavy rain forecasted in other areas including the country's northeast and central regions until May 15.

The progressive liberal Move Forward party won 112 seats in the national poll - far more than the army incumbent's 23 seats - and formed a coalition with former Man City owner Thaksin Shinawatra's Pheu Thai party, which also won 112 seats.

However, the winning party now faces an uphill struggle against an electoral system rigged by the military to ensure army chiefs retain control through a system of 250 military-appointed unelected old-age senators who cast the deciding votes.

The senators - branded 'establishment dinosaurs' by critics - have vowed to reject the Move Forward party and vote for the army to govern.