BANGKOK (AFP) - A Thai property developer was sentenced to 12 years in prison Tuesday (April 5) under the kingdom's royal insult law, the latest conviction linked to a scandal that saw the Crown Prince's ex-wife fall from grace.

Thailand's lese majeste law is one of the world's harshest - carrying up to 15 years in prison per offence - and has increasingly been exercised by the ultra-royalist generals who seized power in a 2014 coup.

Boontham Boonthepprathan, 65, was sentenced for allegedly citing links to the monarchy to ease a land deal nearly 10 years ago.

The judge said his sentence was reduced because of his "useful testimony".

According to the court he also claimed a close connection to Pongpat Chayapun, a senior police officer at the centre of a major corruption probe in 2014 that engulfed many relatives of the Crown Prince's former wife Srirasmi.

Pongpat, Srirasmi's uncle, was accused of running a sprawling criminal syndicate involved in illegal gambling dens, oil smuggling and extortion rackets.

His arrest precipitated a purge that saw at least seven of Srirasmi's other relatives convicted and jailed for lese majeste, including her two elderly parents.

Most were accused of falsely citing links to the monarchy to make money.

Srirasmi renounced her royal title after the scandal and has not been seen in public since.

The affair cast a spotlight on Thailand's largely impenetrable palace affairs, though many of the details remain murky. Both Thai and international media must engage in strict self-censorship when covering the monarchy.

The royal family has become an increasingly sensitive topic as 88-year-old King Bhumibol Adulyadej, the world's longest reigning monarch, enters his twilight years.

Observers say anxiety over the succession has helped fuel the political turmoil of the past decade.

A series of lese majeste accusations in late 2015 saw a famous fortune teller close to Crown Prince Maha Vajiralongkorn jailed over the crime.

He died mysteriously several weeks after being detained in a military prison.

Lese majeste prosecutions have surged under junta rule with record-breaking jail sentences - many in response to social media posts - as authorities broaden their interpretation of the law.