Do I have to pay income tax for the 1st year?

Hi guys, hope I can get some answer to this. I am from Singapore and I will be starting to work in Japan from this July onwards and was wondering about double taxation. My understanding was that once I am in Japan, the taxation will start immediately from my first pay check in July. Concurrently I will still have pay my tax in Singapore. In summary, I will be paying double tax? Is this true and are there way to offset the tax?

What do the tax treaties say? It is quite possible you will be tax resident in two countries at the same time, especially if you have ties still to Singapore, but some countries have "tie-break" rules so you will cease being tax resident in one place, and only in Japan. (That is certainly my situation as my links/assets to NZ - currently not many - would otherwise have me paying two sets of taxes on one set of income.)
As this is a specialist topic, you may need to get specific professional advice unless someone has the exact same circumstance or has looked into it. I'm not intending to learn the details of Singapore tax law to answer this, just providing a hint where to look with the Singapore govt sites/authorities.