どうも Do-u-mo: can be used by itself as casual informal thanks.
ありがとう Arigatou: most casual form, among close friends or to socially lower standing.
どうもありがとうございます Doumo arigatou gozaimasu: casual emphatic form, present tense
ありがとうございます Arigatou gozaimasu: Standard polite everyday form, present tense
ありがとうございました Arigatou gozaimashita: Standard polite everyday form, past tense, thanks for a thing already done; the final i in gozaimashita tends to be unvoiced and may sound more like gozaimash·ta.
どうも Do-u-mo: expresses gratitude or sometimes doubt. This generally softens the meaning and adds emotion. Thus, while どうも (doumo) amplifies gratitude, it can imply a sense of “I’m very grateful, and I’m also humbly aware that I might be imposing a ‘burden’ on you to receive my gratitude, but since we have a closer relationship I am emboldened to express my gratitude openly.” In other words, this softening effect can be interpreted as a slight sense of humility or even a hint of apology for the “burden” of receiving gratitude.
ありがと A-ri-ga-to: derives from the adjective/attribute ありがたい (arigatai, “grateful” or “thankful”), which combines 有り (ari, “to exist/be”) and 難い (katai, “difficult” or “rare”) to originally mean most rare and precious, almost miraculous and astonishing that it should exist.
うございます Go-zo-i-ma-su: (the ‘ü’ of the ending ‘su’ is muted or even silent)
longer vowels tend to sound more polite in Japanese. i and u tend to be unvoiced in busy Tokyo.