Apiruj Suwadee, 72, and his 66-year-old wife Wanthanee are the latest close relatives of fallen former princess Srirasmi to face legal proceedings after a corruption scandal involving her family erupted late last year.
Both had pleaded guilty to insulting the royal family, lodging a malicious claim and asking officials to file false charges against a woman in 2003.
"The judge convicted two defendants on insulting the monarchy and sentenced them to five years in prison," a verdict published by the court stated today.
At least eight of Srirasmi's family have now been convicted and jailed for lese majeste -- her elder sister and brother-in-law, two brothers, a nephew and her parents.
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Another relative, Pongpat Chayapun, the former head of Thailand's elite Central Investigation Bureau, was handed a 31-year jail term for a series of convictions linked to an alleged criminal empire that spanned illegal gambling, extortion and kidnapping. He was initially sentenced to six years for lese majeste.
Srirasmi's siblings were arrested in the wake of that scandal alongside a slew of senior police officers.
According to the court verdict, the Suwadees made false claims about Crown Prince Maha Vajiralongkorn -- who was married to their daughter at the time -- in a bid to threaten their neighbour.
Vajiralongkorn divorced Srirasmi and she renounced her royal title following the scandal, which has gripped a public unused to seeing palace intrigue play out in the open.
She and a younger sister have not been arrested but have retreated from public view.
Experts say the last decade of political turmoil in Thailand is intertwined with concerns among competing elites over the direction of the kingdom once the reign of 87-year-old King Bhumibol Adulaydej comes to an end.
Bhumibol has largely been confined to a Bangkok hospital in recent months, but he made a rare public appearance on Monday.