How about using replace-regexp, which contains optional arguments for START and END? To control lazy highlighting while the search is being performed, the variable query-replace-lazy-highlight can be customized or let-bound to the desired setting; e.g., nil for no lazy highlighting. See also the variables lazy-highlight-initial-delay and lazy-highlight-interval.
(defun chikan ()
"Doc-string."
(interactive)
(replace-regexp "\\<ichi\\>" "one" nil (point-min) (point-max))
(replace-regexp "\\<ni\\>" "two" nil (point-min) (point-max)))
The following example uses an alist (similar to the data structure of a Python dictionary), which is an application requested by the O.P. in a follow-up comment underneath the question hereinabove:
(defun chikan ()
"Doc-string."
(interactive)
(let ((alist '(("ichi" . "one")
("ni" . "two"))))
(dolist (elt alist)
(replace-regexp (concat "\\<" (car elt) "\\>")
(cdr elt)
nil
(point-min)
(point-max)))))
Rather than using word boundary delimiters in the first argument as depicted in this example, see the optional argument in replace-regexp for DELIMITED which contains a doc-string entry as follows: "Third arg DELIMITED (prefix arg if interactive), if non-nil, means replace only matches surrounded by word boundaries. A negative prefix arg means replace backward."
For an answer that deals with regexp matches that excludes surrounding word constituents, see https://stackoverflow.com/a/5941448/2112489 , the text of which is copied hereinbelow for convenience:
The regexp \<foo\> or \bfoo\b matches foo only when it's not preceded or followed by a word constituent character (syntax code w, usually alphanumerics, so it matches in foo_bar but not in foo1).
Since Emacs 22, the regexp \_<foo_bar\_> matches foo_bar only when it's not preceded or followed by a symbol constituent character. A symbol constituent is either a word constituent or a character with syntax _. Most programming mode define _ to be a symbol constituent.