Thank you @Jfish and @water for your replies.
Yes, _ArrayTranspose($myArray) solved my problem. And here's what I tested after reading your replies.
Local $myArray = [1,2,3,4,5]
1)
_ArrayTranspose($myArray)
_Excel_RangeWrite($oExcel, "test_sheet", $myArray, "A1:D1", True, True)
Result: 1 2 3 4 5
2)
_ArrayTranspose($myArray)
_Excel_RangeWrite($oExcel, "test_sheet", $myArray, "A1:D1", True, False)
Result: 1 2 3 4 5
3)
_ArrayTranspose($myArray)
_Excel_RangeWrite($oExcel, "test_sheet", $myArray, "A1")
Result: 1 2 3 4 5
4)
;_ArrayTranspose($myArray)
_Excel_RangeWrite($oExcel, "test_sheet", _ArrayTranspose($myArray), "A1")
Result: 1
5)
;_ArrayTranspose($myArray)
_Excel_RangeWrite($oExcel, "test_sheet", _ArrayTranspose($myArray), "A1:D1")
Result: 1 1 1 1 1
6)
;_ArrayTranspose($myArray)
_Excel_RangeWrite($oExcel, "test_sheet", _ArrayTranspose($myArray), "A1:D1", True, False)
Result: 1 1 1 1 1
7)
;_ArrayTranspose($myArray)
_Excel_RangeWrite($oExcel, "test_sheet", _ArrayTranspose($myArray), "A1:D1", True, True)
Result: 1 1 1 1 1
Before I created this topic, I put _ArrayTranspose() as in 4), 5), 6), 7). Too bad I didn't find example usage of _ArrayTranspose() in _Excel_RangeWrite function reference.
Thanks again for your help.