Deputy army chief Natthapon Nakpanich has emerged as a potential choice for the post of either army chief or defence forces chief with the blessing of Prime Minister Prayut Chan-o-cha, according to a source in the Defence Ministry.
The armed forces are presenting their annual reshuffle lists of senior military officers to Gen Prayut, also defence minister, this week.
The source said the navy and the air force have already submitted their lists to the premier for scrutiny.
The army and the defence forces will hand in theirs after Wednesday, reports suggested on Sunday.
Defence Forces chief Gen Pornpipat Benyasri, who is retiring at the end of next month, is proposing Chalermpol Srisawasdi, chief-of-staff, as his replacement, a source said.
It was also reported that army chief Apirat Kongsompong, also retiring next month, has put forth the name of his assistant, Narongphan Jitkaewtae, as his potential successor.
Both Gen Chalermpol and Gen Narongphan passed the elite King's Guard training and were given a t-shirt with a red rim to signify their completion of the programme.
That was how those trained came to be called the "red-rim" top brass.
The source said that it was customary that the generals vying for the posts of First Army Region commander and the army commander-in-chief received the "red-rim" training.
Also according to the source, Gen Prayut has discussed with Gen Apirat the possibility of promoting Gen Natthapon to either army chief or defence forces chief even though the deputy army chief is not a red-rim top brass.
Gen Apirat told the premier that the red-rim status was not prerequisite to the army top seat.
This led to speculation that Gen Prayut might push Gen Natthapon to be defence forces chief for a year before he goes into mandatory retirement next year.
The source said Gen Natthapon retains close ties to Gen Prayut, having worked under him for a long time.
It was speculated in some quarters that if Gen Natthapon became defence forces chief, he would spend a year in the post until his retirement next year.
In that case, Gen Chalermpol, who has two years left before his retirement, may be appointed deputy defence forces chief for a year before succeeding Gen Natthapon, sources said.
He was also named deputy secretary-general of the now-defunct coup-engineer National Council for Peace and Order, of which Gen Prayut the head.
Gen Natthapon now plays an active role in the Centre for Covid-19 Situation Administration (CCSA).
The deputy army previously dismissed a rumour that he was being shifted to lead the National Security Council (NSC).
He insisted he was not cut out for the job.
In his recent reply to a media question about Gen Natthapon also being considered for the NSC top job, Gen Prayut said it was up to Gen Natthapon.