A Thai woman could be jailed for seven years on charges of sedition after she posted a photo of herself holding a red bowl that had a Thai New Year greeting from siblings and ousted prime ministers Thaksin and Yingluck Shinawatra.

Police ordered Theerawan Charoensuk, 57 and from Chiang Mai in Thailand’s north, to report to a military court on Tuesday to hear a charge for the photos she posted on Facebook, human rights lawyer Anond Nampa told the local Khaosod news website.

Thai New Year, or the Songkran festival, is celebrated every April with major road closures as giant water fights take over the streets. The bowl in the photo, in which Theerawan gives a thumbs up, appears to be a water scoop used during the festival.

Thaksin was ousted in a 2006 coup and his sister, Yingluck, was also removed by the military in 2014. Vitriol between Shinawatra supporters, or red shirts, and the army generals in power, or yellow shirts, has dominated Thai politics for years and at times led to bloodshed in the streets.

That the plastic bowl— which appears to be a promotional item used by supporters of the Shinawatras — is red is significant in Thailand’s colour-coded politics. Another photo posted by the woman shows her holding a 2010 calendar with the Shinawatras on it.

The full message on the bowl is not visible in the photo. Local media said it was signed by Thaksin.

Thaksin has been in self-imposed exile since 2008 to avoid being jailed for corruption on charges he denies. Yingluck is also facing charges that she ignored corruption surrounding a multibillion-dollar rice farming subsidy, although she too denies any wrongdoing.

Junta leader Prayuth Chan-ocha said on Tuesday that Theerawan had threatened national security.

“You have to see: the photo is about a man who broke the law,” Prayuth said, referring to Thaksin, who still has a strong support base in the north among the rural poor. “Isn’t support for a person who broke the laws and ran away from the criminal case a wrong thing to do?”

Deputy prime minister, General Prawit Wongsuwan, also defended the charges: “Tell me if you think what she did was not provocative or led to division in the society. We don’t want to arrest anyone. But those people should listen to our warning not to undertake political activities.”

The military has cracked down hard on any public displays of support for the ousted opposition, arresting activists, politicians and journalists. The junta has warned against any expressions of dissent.

On Tuesday, a military court released Theerawan on 100,000 baht (nearly £2,000) bail pending trial.

New York-based Human Rights Watch said the “draconian” charges showed an utter disregard for peaceful dissent.

“The Thai junta’s fears of a red plastic bowl show its intolerance of dissent has reached the point of absolute absurdity,” said Brad Adams, Asia director. “When military courts try people for sedition for posting photos with holiday gifts from deposed leaders, it’s clear that the end of repression is nowhere in sight.”

The advocacy body said that at least 38 people have been charged with sedition since the coup in May 2014, including former education minister Chaturon Chaisaeng for a speech at the Foreign Correspondents Club of Thailand in which he criticised military rule.