Japan's emperor Akihito met Thailand's new monarch on Sunday during a brief visit to pay respects to his recently departed friend the late King Bhumibol Adulyadej.
The audience was one of the first face to face meetings King Maha Vajiralongkorn has held with a fellow monarch since he ascended the throne following the October death of his father.
Thailand's palace is in a sensitive state of transition and observers are closely watching Vajiralongkorn for any signs over what direction he will take the monarchy during his reign.
Bhumibol was widely loved and sat on the throne for seven tumultuous decades that saw Thailand grow from an impoverished rural nation into a middle income country.
Vajiralongkorn, 64, has spent much of his time outside the kingdom and has yet to attain his father's widespread popularity.
Thailand's nightly royal news programme gave no details on what was said between the two monarchs as they met in Vajiralongkorn?s current Bangkok residence the Dusit Palace.
Both Akihito and his wife Michiko were dressed in black, a colour most Thais will wear for the duration of the one year mourning period until Bhumibol is cremated.
Earlier in the day the Japanese royal couple visited the Grand Palace where Bhumibol's body lies in state ahead of his cremation which is expected to take place at the end of the year.
Hatsuhisa Takashima, Akihito's press secretary, told reporters the Japanese royal couple decided to visit Thailand after a six-day visit to Vietnam because it was "their last occasion to meet with the late king and bid farewell to him".
He said the pair bowed "deeply" in front of Bhumibol's coffin as a mark of respect.
The meeting between Vajiralongkorn and Akihito, a contemporary of Bhumibol, displayed two very different types of Asian monarchies.
In the aftermath of World War Two Japan's royal family was reformed from an institution whose head was once considered a living god into a more contemporary and accountable royal family, albeit one still steeped in religious and palace tradition.
Akihito, 83, has made clear his desire to abdicate with Japanese media reporting that palace officials are planning a 2019 handover to his eldest son.
Thailand's monarchy remains more of a throwback to an earlier era of kings.
Bhumibol was considered near god-like by many Thais while the royal family remains protected from scrutiny or debate by a ferociously enforced less majeste law that has been increasingly wielded in recent years.
Media must heavily self censor as a result.
Bhumibol also signed off on frequent army coups, made key interventions at times of political crises and at other times declined to intervene.
Abdication was never on the cards for Bhumibol who retreated from public view in the last few years of his life -- a time of intense political turmoil -- as he battled successive bouts of ill health.