* Opposition lawmakers say handout plan is unnecessary, risky

* Thai economy lagging regional peers

* Without stimulus, there will be crisis - finance minister

(Recasts with bill passing first vote)

BANGKOK, July 17 (Reuters) - The Thai government's additional 122 billion baht ($3.4 billion) budget bill for the 2024 fiscal year to finance its signature stimulus programme passed its first parliamentary vote on Wednesday.

After a one-day debate by lawmakers to scrutinise the much-criticised handout scheme, the budget passed with 297 votes in favour and 164 against as the Pheu Thai Party-led government commands a majority in the House of Representatives.

The budget will still need to pass second and third readings in the lower house, expected on July 31, before being sent for senate and royal approval.

"The government needs the budget to stimulate the economy by boosting money circulation in various areas," Prime Minister Srettha Thavisin told parliament.

The 500 billion-baht ($13.9 billion) scheme is aimed at jump-starting Southeast Asia's second-largest economy, which grew only 1.9% last year and has trailed regional peers.

Srettha said the economy was expected to grow 2.5% this year and extra budget spending would adhere to fiscal discipline.

The scheme, a giveaway of 10,000 baht each to 50 million Thais to be spent locally, has been delayed to the fourth quarter of this year due to issues finding funding sources.

"There is a need to stimulate the economy," Finance Minister Pichai Chunhavajira said during the parliamentary debate.

"If nothing is done, there will definitely be a crisis."

The government said on Monday it had the approval of an intra-agency committee to use 2024 and 2025 budgets for the so -called "digital wallet" programme.

The panel includes members of the central bank, which has voiced concern about the programme and has recommended it be more narrow and focused on the poor.

The stimulus plan was the Pheu Thai Party's flagship policy in the 2023 election and has been criticised by economists and two former central bank governors for being fiscally risky, which the government rejects.

Opposition lawmaker Sirikanya Tansakul questioned whether the handout programme was necessary and said the funds could be better kept for emergencies.

"We increase the fiscal risks for the country. Right now, we don't have room to deal with emergency situations," Sirikanya said during the debate.

The budget debate comes as Srettha faces a Constitutional Court case that could potentially lead to his dismissal over one of his cabinet appointments. The prime minister denies wrongdoing. ($1 = 36.04 baht) (Reporting by Orathai Sriring, Thanadech Staporncharnchai and Panarat Thepgumpanat; Editing by Martin Petty and Emelia Sithole-Matarise)