thin: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/thin - from package: rubygem-thin
/usr/lib/ruby/gems/1.8/gems/thin-1.2.8/bin/thin - from package: rubygem-thin

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/thin - from package: thin

You may install the required package with command apt-get install {package}

Error in other languages:
thin: bevel nie gevind nie
thin: comandă negăsită
thin: comando não encontrado
thin: commande introuvable
thin: command not found
thin: käsku ei ole
thin: không tìm thấy lệnh
thin: komanda nerasta
thin: Kommando nicht gefunden.
thin: kommandot finns inte
thin: komut yok
thin: nie znaleziono polecenia
thin: níor aimsíodh an t-ordú
thin: no se encontró la orden
thin: no s'ha trobat l'ordre
thin: opdracht niet gevonden
thin: parancs nem található
thin: perintah tidak ditemukan
thin: príkaz nenájdený
thin: příkaz nenalezen
thin: команда не найдена
thin: командата не е открита
thin: 命令找不到
thin: コマンドが見つかりません