Lesotho's high court will decide if Prime Minister Thomas Thabane can claim immunity from a charge that he murdered his wife prior to marrying his present spouse in a case that has gripped this tiny southern African country.

Thabane, 80, appeared in court in the capital Maseru in a pre-trail hearing on Monday alongside his present wife Maesaih.

He is suspected of involvement in the murder of his then wife Lipolelo, who was shot dead in June 2017 two days before he took office for a second stint as premier and two months before he married Maesaiah.

He and Lipolelo were going through divorce proceedings.

Maesaiah Thabane, 42, has been charged with the murder, and police suspect her of ordering assassins to do the job.

Both deny any involvement.

Crowds of supporters packed the magistrates' court and gathered outside for Monday's hearing. Thabane, wearing a blue striped suit and a powder blue shirt, looked tense. Maesaiah Thabane sat beside him in a floral dress and bucket hat.

No charges were read out and his lawyer argued the case should be referred to the high court to answer a question of possible immunity, which magistrate Phethise Motanyane granted.

Thabane has said he will resign at the end of July, while several members of his own All Basotho Convention (ABC) party have been pressuring him to go sooner to avert political chaos.

A potential plea of immunity would likely raise doubts over how willing he is to step down, further fanning the political crisis in this mountain territory of 2-million people.

Police had initially intended to charge Thabane on Friday, but he left the country for a medical appointment.

Lesotho, which is surrounded on all sides by South Africa, has a history of coups and political instability that has often led its bigger neighbour to intervene and restore order.