What is a unique, entertaining idea of something to do in Chiang Mai while it is raining?

Offer a prayer of thanks

Take off your clothes and go for a motorcycle ride..........

Go for a massage, or a drink, or both. Oh wait, that's the same as when it's sunny.

A friend of mine back home used to say

Do like they do in the old country let it rain.

It of course is better with the thunder and lightening show.

Go see a movie.

Get upside down pissed and stagger in to a karaoke bar.

Make nonsensical posts on TV?

My favourite time for photography.

... go singing, and dancing in the ....

Isn't it great. More time to sleep in, cuddle up ...the garden grows all by itself. Car needs a wash more often but hey, less dust in the house!

Wife has less to do so it's off shopping ... can't win either way!

Ummmmm, there's the usual suspects;

Drinking, massage, encounters, or there's apparently the Grand Opening of the Promenada Mall? 555555555

You obviously came to the right place for good advice !!!

Singing In The Rain

Count all the one baht and satang coins lying somewhere in the house and go enjoy a 30 baht Khao Soy Noodles

The word "unique' in the original post negates the answers so far.

Design a logo for yourself or a family coat of arms.

Write a poem or song, or compose a symphony.

Draw a tree or paint a self portrait.

Invent a new language.

Of course although these are all unique the act of doing them is not unique. Hopping backward to say Chiang Dao from Chiang Mai might be a unique act but is hopping backward unique?

Hang about - it's stopped raining - I'm outa here! Goin' bowling.

go shopping at all the new malls??????