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The 37-year-old announced today on Instagram that he had successfully completed 'day one' with the Super Rugby side ahead of their season opener against the Blues this month and was ''grateful for the incredible opportunity''.
Thomson has joined the Chiefs as one of eight replacement players currently in with the squad.
"It's a strange old beast this life we live, this time two years ago I was flat on my back in a Japanese hospital unable to walk," Thomson posted on Instagram. "So never underestimate what the human body can do with a little self belief and a whole lot of hard work - persistence pays."
"Day 1 done, but we're just getting started. Rent's due. Let's go to work!"
Thomson said: "I am really excited to work under Gats [coach Warren Gatland] and I am also excited to be in a team like the Chiefs. It's a team I've always looked up to, especially playing against them. The flare that they bring and the excitement. They seem like they have a lot of fun out there which is always a team you want to be involved with. If I get an opportunity to play for the team it'll be immense."
Thomson was admitted to Tsukuba Memorial hospital in Tokyo on December 19 2017, with an illness that left him unable to walk for days and initially had doctors baffled.
He posted from his hospital bed during Christmas 2017 saying he had a long road to recovery ahead after being rushed to hospital in "excruciating pain".
He was later diagnosed with lumbar discitis — an infection in the intervertebral disc space.
"New year, new jersey... Last week I was camping in the MacKenzie Country for some overdue kiwi-summer family time. Today I pulled on this jersey and mixed it up with 8 current allblacks and a superrugbynz side stacked with talent!"
Thomson left New Zealand at the end of the 2012 Super Rugby season after 68 appearances for the Highlanders to take up a contract with the Canon Eagles in Japan.
He returned to Super Rugby in 2015 and '16, playing for the Reds and Rebels respectively, before going back to Japan, linking back up with the Canon Eagles.
In 2017 he joined the NEC Green Rockets in the Japanese Top League, and lat year re-signed with Otago for a stint of several weeks.
As well as taking the field for the All Blacks, Thomson represented New Zealand at secondary schools, under-19, under-21 and Sevens levels.