BANGKOK, Aug. 31 (AFP) - Thailand delayed on Monday its US$724 million purchase of two submarines from China, following public outrage over the controversial deal as the kingdom's economy flatlines due to the coronavirus pandemic.

Under a 2015 deal, Thailand was one of the first countries to buy Chinese naval hardware and finalised its purchase of three submarines in 2017, with the first one expected to be delivered in 2023.

An order for two more for 22.5 billion baht (US$724 million) was approved earlier this month by a parliamentary sub-committee - a move which drew public outcry as Thailand struggles with a freefalling economy.

Angry Thais took to social media to criticise the deal, and the hashtag "People don't want submarines" trended on Twitter.

Government spokesman Anucha Burapachaisri announced Monday Prime Minister Prayut Chan-o-cha - also defence minister - had "requested the navy to consider a delay" in the purchase of the two additional submarines.

"The navy will negotiate with China to delay for another year," Anucha told reporters.

Prayut's military-aligned administration is under fire from near-daily protests demanding his resignation and a complete overhaul of the government - which the demonstrators consider illegitimate.

Thailand's economy is also undergoing one of its worst periods in more than 20 years, contracting 12.2 per cent in the second quarter as its tourism - and exports-led sectors have been hard-hit by the pandemic.

"The prime minister has given priority to the concern of the public who are worried about the economy," Anucha said.

Besides questioning military purchases and the government's handling of the economy, the burgeoning pro-democracy movement is also calling for reforms to the unassailable monarchy - a once-taboo topic in the kingdom.

The increasingly bold requests from the youth-led protesters have drawn ire from arch-royalist camps, who have held counter-demonstrations to demand that protesters "do not touch the monarchy".

More than a thousand mostly older demonstrators dressed in yellow shirts - considered a royal colour - massed at a stadium Sunday, holding portraits of the super-rich King Maha Vajiralongkorn.

On Monday, they submitted a letter to the Japanese embassy in Bangkok to demand the extradition of prominent government critic Pavin Chachavalpongpun, who started a private Facebook group to hold frank discussions of the monarch.