Trump in Asia: A beginner's guide to trade, threats and tweets

US President Donald Trump is on his first official trip to Asia, passing through Japan, South Korea, China, Vietnam and the Philippines.

From trade to etiquette, each stop will have its own challenges. So here is a (non-exhaustive) beginner's guide to the issues at stake.

Mr Trump starts off by visiting Washington's closest Asian friends: Japan and South Korea. But it's North Korea they will be talking about. Pyongyang has already sent two long range missiles over Japan and conducted its sixth and biggest nuclear test. Despite harsher sanctions, North Korean leader Kim Jong-un has shown no sign of slowing down the pace of weapons development. Skittish observers wonder if the visit will prompt Pyongyang to do something rash. But if talks with almost every leader are about how to deal with North Korea, there is unlikely to be any real consensus. Here are some key questions from this leg of the trip:

How much reassurance can Trump provide? With Japanese citizens rehearsing drills in case of a nuclear attack, Tokyo will want to know the US will provide military co-operation. Seoul, literally in the firing line of its northern neighbour with artillery positioned over the border, will want the same.

Will Trump tweet while so close to the North? After an unprecedented personal warning to Mr Trump from Kim Jong-un, Seoul will want him to tone down his rhetoric and keep options for dialogue open. Any threats exchanged when he is literally over the border won't go down well.

How will he like the viral Pen Pineapple song? In Tokyo he is also set to meet Piko Taro, singer of the Pen-Pineapple-Apple-Pen earworm that swept the globe.

What about that awkward handshake? Mr Trump and Japan's PM Shinzo Abe are thought to have a strong relationship, but people will watch closely after the patting and twitching of their last 19-second handshake.

China is North Korea's chief economic supporter and Mr Trump is likely to seek continued support for sanctions. But Chinese leader Xi Jinping has just emerged from a Communist Party Congress that saw his power reach unprecedented levels, so he may not feel the need to compromise. Few observers expect radical shifts in the US-China relationship, but they will be watching for any clues to shifts in the global balance of power. China set out its stall earlier this year with a push to its 2013 Belt and Road project, a vast global trade network with China at its heart. Here are other things to look out for:

Will he assert US military dominance? The South China Sea dispute may have been quiet over the last few months as North Korea rumbled, but nonetheless China is going ahead with development in the disputed sea.

Will he talk tough on trade? Mr Trump is known for lambasting China over allegedly unfair trade policies, currency manipulation and stealing US jobs. He has just called the US trade deficit with China "embarrassing" but what can he achieve in practice?

Will Chinese social media meme the meet? Chinese social media is known for its creative memes (remember the Winnie the Pooh and Tigger memes when Mr Xi met President Obama?) Will they move faster than the censors this time?

By the time Mr Trump gets to Vietnam and the Philippines we should know more about how the US is positioning itself in Asia. Trade is likely to be key. Mr Trump pulled out of the Trans-Pacific Partnership (TPP) free trade deal, frustrating many, including Vietnam, his host at the Asia Pacific Economic Cooperation (Apec) Economic Leaders' meeting.

Even Japan and Korea are nervous the US will back off from bilateral trade agreements. His "America First!" slogan is aimed at a domestic audience but does not go down well with trade partners abroad. And there are other questions from this leg:

Will he speak out on human rights? Both Vietnam, which puts dissenting bloggers in jail, and the Philippines, with its controversial drug war, have a patchy rights record - but will Mr Trump speak out?

What happens when Trump and Duterte meet? They are the two most outspoken leaders in the world, so expect colourful talk. But Philippine President Rodrigo Duterte has shown he is just as willing to woo China as the US, the Philippines' traditional ally.