Consider 2 Thai words

1)เทพ 2)เทป

The 1st follows the tonal rules to produce a predictable FALLING tone. It has that tone.

The 2^nd has all the same tonal elements as the 1^st and yet produces a HIGH tone.

Any explanations out there?

Technically both have a falling tone but as เทป is a loan word (tape) maybe some pronounce it as a short tone therefore high.

Just a guess.

In my opinion, tape เทป is an english word that they pronounce it on a different way. Sometimes the tone rules don`t apply to words of foreign origin. It is as simple as that.

Sounds about right-Thanks

I just listened to some sound files in my dictionary from native Thai speakers saying words like เทปกาว ตลับเทป สก๊อตเทป ฯลฯ and เทป appears to be high tone, long vowel length.

As Khun Katna tells us, Thai people often do not pronounce foreign sourced words the way they tend to be written in the dictionary. See Lexitron's entry for เทป: "เทป /tʰéːp/ [N] tape" where the high tone is indicated.

However, this disparity may be disappearing. In the Royal Institute's "Dictionary of New Words, Volume I" (พจนานุกรมคำใหม่ เล่ม๑) the introductory section states:

"๓.๑ คำที่ยืมมาจากภาษาต่างประเทศเขียนตามเสียงที่คนไทยส่วนใหญ่ออก เช่น . . . เหรตติ้ง . . . (อ. rating)." [Note the low tone in the first syllable and the falling tone in the second syllable of the word เหรตติ้ง.]